There's not a moment of our lives when smells -- or, more precisely, odor molecules -- aren't impacting our brain. It's been estimated that it takes at least 40 molecules of a given odor for us to be aware of a smell. But each one of our receptor cells can fire in response to as little as a single odor molecule wafting through the air. So even if we think we're not smelling anything, our brain may disagree.

Many studies have shown that your brain reacts to smells whether or not you're aware of them. Undetected odors can alter your brain's electrical activity, according to EEG readings, and can trigger measurable physiological reactions such as changes in body temperature and heart rate. In one experiment, the part of the brain that reacted to the odor molecules was a region responsible for focusing attention and directing awareness. It seems that our brain may be aware of smells and attending to them whether or not our conscious mind is paying attention!

98

About the Author

David Gamon, PhDDr. David Gamon, one of the original writers at ScienceIQ, studied
cognitive science at U.C. Berkeley, where he received his Ph.D. in
Linguistics in 1997. He is the author of many popular books about the
human brain, including Building Mental Muscle, Use It Or Lose It!, and Brains That Work a Little Bit Differently. His current projects include books about gender differences in the brain, the brain’s construction of sensory reality, and psychopathy.